HVDC Kingsnorth was a high-voltage direct-current (HVDC) transmission system connecting Kingsnorth in Kent to two sites in London. It was at one time the only application of the technology of high voltage direct current transmission for the supply of transformer stations in a city, and the first HVDC link to be embedded within an AC system, rather than interconnecting two asynchronous systems. It was also the first HVDC scheme to be equipped with self-tuning harmonic filters and to be controlled with a "Phase Locked Oscillator", a principle which subsequently became standard on all HVDC systems. [1]
It was designed in the late 1960s and went into service in 1974. [2] It ran from Kingsnorth power station as a 59 kilometers long bipolar (3-wire) underground cable. The positive pole operating at a voltage of +266 kV terminated at the converter station in Beddington near Croydon. The negative pole continued to run a further 26 kilometers at -266 kV line to a similar station at Willesden in North London.
There was also the possibility, if the converter station in Kingsnorth was out of service, to run the system as monopolar HVDC between the Beddington and Willesden stations. The HVDC Kingsnorth was one of the last HVDC schemes equipped with mercury vapour rectifiers, which were ARAG/4-valves designed by English Electric. Each converter station for 266 kV consisted of two six-pulse valve bridges for 132 kV switched in series, which were each fed via a star-star and a star-delta connected transformer.
Apart from the Nelson River Bipole 1 system in Canada, all later-built HVDC systems used thyristor valves. The Kingsnorth HVDC scheme could transfer a maximum power of 640 megawatts (320 megawatts per pole).
In 1981, one mercury arc valve at Willesden Static Inverter Plant, was replaced by a H200 thyristor valve, developed by English Electric.
The system described was shut down in 1986 [2] or 1987 [3] following system reinforcement on the network it was embedded in. However the capacitor banks located at Kingsorth were used for voltage control on the network. These were later removed from the system completely in the mid 1980s? (1990s?) as they contained PCB.
Site | Coordinates |
---|---|
Kingsnorth converter station (out of service) | 51°25′11″N0°35′46″E / 51.41972°N 0.59611°E |
London-Beddington converter station (out of service) | 51°22′23″N0°7′38″W / 51.37306°N 0.12722°W |
London-Willesden converter station (out of service) | 51°32′03″N0°15′29″W / 51.53417°N 0.25806°W |
A high-voltage direct current (HVDC) electric power transmission system uses direct current (DC) for electric power transmission, in contrast with the more common alternating current (AC) transmission systems.
The HVDC Volgograd–Donbass is a 475 kilometres (295 mi) long bipolar ±400 kV high voltage direct current powerline used for transmitting electric power from Volga Hydroelectric Station at Volgograd in Russia to Donbas in eastern Ukraine and vice versa.
The HVDC Cross-Channel is the 73-kilometre-long (45 mi) high-voltage direct current (HVDC) interconnector that has operated since 1986 under the English Channel between the continental European grid at Bonningues-lès-Calais and the British electricity grid at Sellindge. The cable is also known as IFA, and should not be confused with the new IFA-2, another interconnect with France that is three times as long but only half as powerful.
The HVDC Inter-Island link is a 610 km (380 mi) long, 1200 MW high-voltage direct current (HVDC) transmission system connecting the electricity networks of the North Island and South Island of New Zealand together. It is commonly referred to as the Cook Strait cable in the media and in press releases, although the link is much longer than its Cook Strait section. The link is owned and operated by state-owned transmission company Transpower New Zealand.
The Pacific DC Intertie is an electric power transmission line that transmits electricity from the Pacific Northwest to the Los Angeles area using high voltage direct current (HVDC). The line capacity is 3.1 gigawatts, which is enough to serve two to three million Los Angeles households and represents almost half of the Los Angeles Department of Water and Power (LADWP) electrical system's peak capacity.
The Nelson River DC Transmission System, also known as the Manitoba Bipole, is an electric power transmission system of three high voltage, direct current lines in Manitoba, Canada, operated by Manitoba Hydro as part of the Nelson River Hydroelectric Project. It is now recorded on the list of IEEE Milestones in electrical engineering. Several records have been broken by successive phases of the project, including the largest mercury-arc valves, the highest DC transmission voltage and the first use of water-cooled thyristor valves in HVDC.
Cahora-Bassa is a separate bipolar HVDC power transmission line between the Cahora Bassa Hydroelectric Generation Station at the Cahora Bassa Dam in Mozambique, and Johannesburg, South Africa.
The Inga–Shaba EHVDC Intertie is a 1,700 kilometres (1,100 mi)-long high-voltage direct current overhead electric power transmission line in the Democratic Republic of Congo, linking the Inga hydroelectric complex at the mouth of the Congo River to mineral fields in Shaba (Katanga). It was primarily constructed by Morrison-Knudsen International, an American engineering company, with the converter equipment supplied by ASEA. Construction was completed in 1982 and it cost US$900 million. The scheme was, for many years, the longest HVDC line in the world.
An HVDC converter station is a specialised type of substation which forms the terminal equipment for a high-voltage direct current (HVDC) transmission line. It converts direct current to alternating current or the reverse. In addition to the converter, the station usually contains:
A valve hall is a building which contains the valves of the static inverters of a high-voltage direct current plant. The valves consist of thyristors, or at older plants, mercury arc rectifiers. Mercury arc rectifiers are usually supported by insulators mounted on the floor, while thyristor valves may be either supported by insulators or hung from the roof of the valve hall. The latter required a stronger ceiling structure, however the hall and the static inverter can better survive earthquakes compared to valve structures standing on the floor.
A mercury-arc valve or mercury-vapor rectifier or (UK) mercury-arc rectifier is a type of electrical rectifier used for converting high-voltage or high-current alternating current (AC) into direct current (DC). It is a type of cold cathode gas-filled tube, but is unusual in that the cathode, instead of being solid, is made from a pool of liquid mercury and is therefore self-restoring. As a result mercury-arc valves, when used as intended, are far more robust and durable and can carry much higher currents than most other types of gas discharge tube. Some examples have been in continuous service, rectifying 50-ampere currents, for decades.
The HVDC Itaipu is a High-voltage direct current overhead line transmission system in Brazil from the Itaipu hydroelectric power plant to the region of São Paulo. The project consists of two ±600 kV bipoles, each with a rated power of 3150 MW, which transmit power generated at 50 Hz from the Paraguay side of the Itaipu Dam to the Ibiúna converter station near São Roque, São Paulo. The system was put in service in several steps between 1984 and 1987, and remains among the most important HVDC installations in the world.
The HVDC Haenam–Cheju is a 101 kilometer long HVDC submarine cable connection between the Korean Peninsula and the island of Jeju in South Korea, which went into service in 1996. The connection is bipolar, consisting of two 180kV cables with a maximum transmission power of 300 megawatts.
The HVDC Rihand–Delhi is a HVDC connection between Rihand and Dadri in India, put into service in 1990. It connects the 3,000 MW coal-based Rihand Thermal Power Station in Uttar Pradesh to the northern region of India. The project has an 814 kilometres (506 mi) long bipolar overhead line. The transmission voltage is 500 kV and the maximum transmission power is 1,500 megawatts. The project was built by ABB.
HVDC BorWin1 is the first HVDC facility in the world to be built for importing power from an offshore wind park to shore, and the first to use voltage source converters (VSC) in Germany. It connects the offshore wind park BARD Offshore 1 and other offshore wind farms in Germany near Borkum to the European power grid. The facility was built by ABB and has a capacity of 400 MW at a bipolar voltage of ±150 kV. HVDC BorWin1, which leads from BorWin Alpha Offshore Platform to Diele substation, consists of a 75 kilometres (47 mi) of underground and 125 kilometres (78 mi) of submarine cable.
The Vizag back-to-back HVDC station, or Visakhapatnam back-to-back HVDC station, is a back-to-back HVDC connection between the eastern and southern regions in India, located close to the city of Visakhapatnam, and owned by Power Grid Corporation of India.
The Chandrapur back-to-back HVDC station is a back-to-back HVDC connection between the western and southern regions in India, located close to the city of Chandrapur. Its main purpose is to export power from the Chandrapur Super Thermal Power Station to the southern region of the Indian national power grid. It is owned by Power Grid Corporation of India.
The Chandrapur–Padghe HVDC transmission system is an HVDC connection between Chandrapur and Padghe in the state of Maharashtra in India, which was put into service in 1999.
An HVDC converter converts electric power from high voltage alternating current (AC) to high-voltage direct current (HVDC), or vice versa. HVDC is used as an alternative to AC for transmitting electrical energy over long distances or between AC power systems of different frequencies. HVDC converters capable of converting up to two gigawatts (GW) and with voltage ratings of up to 900 kilovolts (kV) have been built, and even higher ratings are technically feasible. A complete converter station may contain several such converters in series and/or parallel to achieve total system DC voltage ratings of up to 1,100 kV.
The Xiangjiaba–Shanghai HVDC system is a ±800 kV, 6400 MW high-voltage direct current transmission system in China. The system was built to export hydro power from Xiangjiaba Dam in Sichuan province, to the major city of Shanghai. Built and owned by State Grid Corporation of China (SGCC), the system became the world’s largest-capacity HVDC system when it was completed in July 2010, although it has already been overtaken by the 7200 MW Jinping–Sunan HVDC scheme which was put into operation in December 2012. It also narrowly missed becoming the world’s first 800 kV HVDC line, with the first pole of the Yunnan–Guangdong project having been put into service 6 months earlier. It was also the world’s longest HVDC line when completed, although that record is also expected to be overtaken early in 2013 with the completion of the first bipole of the Rio Madeira project in Brazil.
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